Tier-2 to Tier-2 Data Transfer Link Commissioning Procedures

DRAFT IN PROGRESS

Motivation

New CMS Tier-2 sites should commission PhEDEx data transfer links to and from Tier-1 and all other Tier-2 sites in CMS. Since there are ~50 Tier-2 sites, or ~100 transfer links from a new Tier-2 to and from all other Tier-2 sites, this process will go much more quickly if the data administrators of the new site can carry out much of the day-to-day commissioning tasks. This twiki outlines the procedures, metrics and usual challenges in commissioning Tier-2 to Tier-2 links.

PhEDEx Site Commissioning

Instructions for setting up PhEDEx at a new site can be found here. Before commissioning Tier-2 to Tier-2 links, the site should have commissioned all the Tier-1 links to and from their site.

Setting up the Tier-2 to Tier-2 LoadTest

Subscriptions

To be used in the Production instance of PhEDEx, a data transfer link must first go through a commissioning procedure in the Debug instance using the LoadTest infrastructure. Subscription requests should be made in PhEDEx for LoadTest samples over every Tier-2 to Tier-2 link in both directions. This is best accomplished with:

  • A subscription to the commissioning Tier-2 to download the LoadTest samples from every other Tier-2.
  • A second subscription to every other Tier-2 to download the LoadTest sample from the commissioning Tier-2.

Injections

Unlike Production instance data transfers, the LoadTest injects new replicas at pre-set rates. A Tier-2 site can in general only set the injection rates from their site. As a baseline, injection rates should be set to 0.03 MB/s, which corresponds to at least one file per day per link.

  • Sites will need to ask centrally that injection rates be set to the baseline for links to your site.

Metrics for Commissioning

To become a commissioned link in the Production instance of PhEDEx, allowing real Production data transfers between sites, a link must pass a commissioning metric. The metric for Tier-2 to Tier-2 links is:

  • 5MB/s average transfer rate in 24h, i.e. transfer 422 GB (typically 169 files of 2.5GB each) in less than 24h.

Procedures

Sites can initiate commissioning of links from their site to begin the procedure:

  • Choose a link to another Tier-2 site that has successfully transferred files (with 100% success) in the past day or so (see the PhEDEx rate page).
  • Inject ~200 files on this link from the Injection page.
  • Check back in several hours and see if the ~200 files have successfully transferred.

If the files successfully transferred in less than 24h, the link will be autumatically activated in the Production instance within the next 24h. Choose another link and commission it.

Once all the Tier-2 links from your site are commissioned, please contact central operations to initiate injections to commission links to your site.

Problems

-- JamesLetts - 04-Apr-2012

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Topic revision: r4 - 2012-04-05 - JamesLetts
 
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